Factors Affecting Rate of Photosynthesis 2

When photosynthesis takes place, plants use the suns energy to combine carbon dioxide from the air with water from the soil to create glucose (a carbohydrate)....

05/01/2018 · What factors affect photosynthesis

There are three main factors that affect the rate of photosynthesis

Linseed () meal is the by-product ofextracting the seed for oil. The meal contains 350-380 g/kg CP that is low inprotein quality, being deficient in lysine. It has been a favourite proteinsource for horses and ruminants in the past. Today, soya meal is preferred as itis cheaper and of higher protein quality. The meal fed in large amounts islaxative, and excess amounts in rations have undesirable softening effects onbutterfat and give milk a rancid taste. The recommended maximum intake forcattle is 3 kg per day. Because of this softening property of the oil, linseedcake is unsatisfactory as a main ingredient in pig feeds. Up to 1 kg per day hasbeen used with good results, but not more than 8 percent linseed meal iscommonly included in rations. For young pigs and brood sows a maximum of 5percent linseed meal in the ration is usually recommended. Linseed meal is toxicto poultry except in very small proportions (under 3 percent). Larger amountsdepress growth. The toxicity can largely be eliminated by soaking the meal inwater for twenty-four hours or by adding pyridoxin, one of the B-vitamins to thediet (FAO, 2001c).

Factors Affecting The Rate Of Photosynthesis - Google …

The results of this experiment suggested that the performance in terms of tolerance to water stress and maintenance of root growth during a water deficit was similar in seedlings of small and big size, even under temperatures warmer than those generally occurring in typical boreal forests dominated by black spruce. Moreover, delayed stomatal closures were observed to occur in smaller seedlings, which allowed higher rates of photosynthesis to be maintained than in bigger seedlings. Given the financial and logistic advantage of using smaller seedlings in artificial regeneration, their utilization should be seriously considered and tested in boreal stands experiencing occasional drought events or non-optimal soil moisture conditions.

Factors Affecting The Rate Of Photosynthesis - Google Sites

The growth of new roots is a key factor for the successful establishment of seedlings after planting. The definitive establishment allows a sufficient rate of water and nutrient uptake to be sustained in the long term or during stressful events, which can occur early and frequently in boreal forests (, ). Root growth can be affected by water stress that inhibits division and differentiation of the cells at the apical meristem of roots (). Root growth is also related to the availability of photosynthates for meristem development (). Under similar environmental conditions and water potentials, the smaller seedlings demonstrated an ability to maintain higher rates of gas exchanges than the other seedlings. Delayed stomatal closures ensure the CO2 assimilation for completing the photosynthetic process even under unfavorable environmental conditions. Accordingly, the slope of the regression for C25 was steeper than those estimated for the other seedling sizes, suggesting higher growth rates in smaller seedlings. However, no statistical difference in root growth was observed during the treatment. Thus, it was concluded that root growth in smaller seedlings was comparable to that observed in the other seedling sizes.

Physiological factors that affect photosynthetic rates

C25 had the lowest root density compared to seedlings of the bigger sizes, indicating that in proportion, a higher volume of soil was available for the roots of smaller seedlings, which have lower needle biomass and consequently need less water for the evapotranspiration process (, ). The lower shoot:root ratio of smaller seedlings could also explain their ability to sustain an appropriate water status of the tissues. Increasing shoot:root ratios indicate the occurrence of higher proportions of leaves in respect to roots, whose biomass could be insufficient or less adequate to satisfy the water requirements for maintaining gas exchanges and photosynthesis. According to Bernier et al. () the previous statement concerns bare-root seedlings and should be taken with caution in the case of containerized seedlings, which should experience no limiting factor. However, the container itself may represent a physical factor constraining root growth, as also deduced by the higher root density observed in C350 with respect to C25. It is well known that water absorption efficiency and seedling survival are negatively affected at high root densities (, ). Moreover, although the biomass of each compartment increased according to the seedling size, bigger seedlings invested more in producing needles than roots, thus modifying the proportion between roots and needles (compare the dry weight of needles and roots in ).

"Three factors can limit the speed of photosynthesis: ..

When exposed to excess light, leaves must dissipate the surplus absorbed light energy so that it does not harm the photosynthetic apparatus. Heat production and the xanthophylls cycle appears to be important avenues for dissipation of excess light energy. The xanthophylls cycle comprises the three carotenoids violaxanthin, antheraxanthin, and zeaxanthin. Experiments have shown that zeaxanthin is the most effective of the three xanthophylls in heat dissipation. The zeaxanthin content increases at high irradiances and decreases at low irradiances. In leaves growing under full sunlight, zeaxanthin and antheraxanthin can make up 60% of the total xanthophyll cycle pool at maximal irradiance levels attained at midday (). Contrary to the diurnal cycling of this pool observed in summer, zeaxanthin levels remain high all day during the winter. Presumably this mechanism maximizes dissipation of light energy, thereby protecting the leaves against photooxidation during winter.

Factors effecting photosynthesis

The highest photosynthetic rates seen in response to increasing temperature represent the . Optimal temperature is the point at which the capacities of the various steps of photosynthesis are optimally balanced, with some of the steps becoming limiting as the temperature decreases or increases. Membrane-bound electron transport processes become unstable at high temperatures, cutting off the supply of reducing power and leading to a sharp overall decrease in photosynthesis. Optimal temperatures have strong genetic (adaptation) and environmental (acclimation) components. Plants of different species growing in habitats with different temperatures have different optimal temperatures for photosynthesis. Plants growing at low temperatures maintain higher photosynthetic rates at low temperatures than plants grown at high temperatures.

Photosynthesis factors affecting rate ..

In the presence of adequate amounts of light, higher CO2 concentrations support higher photosynthetic rates. The reverse is also true: low CO2 concentrations can limit the amount of photosynthesis in C3 plants. Carbon dioxide is a trace gas in the atmosphere, presently accounting for about 0.039%, or 390 parts per million (ppm), of air. Currently the CO2 concentration of the atmosphere is increasing by about 1 to 3 ppm each year. By 2100 the atmospheric CO2 concentration could reach 600 to 750 ppm unless fossil fuel emission are controlled. Carbon dioxide and methane, play a role similar to that of the glass roof in a greenhouse. The increased CO2 concentration and temperature associated with the greenhouse effect can influence photosynthesis. At current atmospheric CO2 concentrations, photosynthesis in C3 plants is CO2 limited, but this situation could change as atmospheric CO2 concentrations continue to rise. Under laboratory conditions, most C3 plants grow 30 to 60% faster when CO2 concentration is doubled (to 600-750 ppm), and the growth rate becomes limited by the nutrient available to the plant.